Extinction of Species. — McCreery. 108 
in streams flowing north into lake Erie. Tliere had heen a 
summer freshet some days before, but the water was then low. 
I found thousands of dead shells but not a single live one in 
four miles walking in the bed of the stream. The fresh water 
mussels bur}'- themselves with one end of the shell just pro- 
jecting above the sand and gravel, and the end in which the 
openings are located directed up stream. The valves are 
usually slightly parted so that the water may enter through 
one siphon and after the animalcules, etc., contained in the 
water have been strained out by the gills of the mussel, the 
water is forced out through the outlet siphon. But the sum- 
mer freshet had washed so much sand into the opening of the 
shells that the mussel was unable to close the valves, and so 
an animal that spends its whole life in the water was drowned 
in its native element. Visits to the locality several times since 
show that they have notyet recovered their former abundance, 
and nothing would be necessary to totally extinguish all the 
species of Unio in northern Ohio but frequent summer fresh- 
ets continued from year to year. 
A few years ago about three miles south of this city there 
was a swamp in which a particular species of snail Helix 
mitchelliana^ was found. It has not been found elsewhere in 
northern Ohio up to this time so far as known. To say that 
it was plentiful gives but a faint idea of its abundance. Per- 
haps the fact that at one visit of a couple of hours I collected 
more than a quart may give an idea of the numbers. Three 
years after the discovery of this interesting colony a ditch was 
dug round the swamp which drained the surface of the field 
and cut off the supply of water from the water-loving plants 
which covered its surface, causing thd death of the swamp 
vegetation. As this snail is a vegetarian, the disappearance of 
the swamp vegetation may have destroyed its suppl}" of food, 
or the lack of proper shelter, or more likely a combination of 
many slight causes may have exterminated it ; at any rate the 
snails totally disappeared and the most careful search all 
round the vicinity has failed to find a single specimen since. 
Five or six years ago in one of the lumber yards of this city 
there was a minute species of snail, Pupa corticariea, not yet 
elsewhere reported in this vicinit3^ It had ])robably been in- 
troduced here attached to pine lumber from Michigan where 
this species is connnon. The surface of the lumber yard was 
